JP2017009441A - Inertial force sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection element capable of preventing a wafer from being damaged in manufacturing stage.SOLUTION: The inertial force sensor having a detection element. The detection element includes: a first base plate; a second base plate formed over the first base plate; a third base plate formed over the second base plate. The third base plate includes: a support part; an arm part connected to the support part; a weight part connected to the arm part; and a peripheral part formed on the periphery of the arm part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inertial force sensor using a vibrator in an electronic device or the like.

  2. Description of the Related Art Conventionally, there is known an inertial force sensor in which a vibrator and a support base that supports the vibrator are formed by being separated from a wafer.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2012-237653 A

  Conventionally, in the manufacturing process of the angular velocity sensor element, the outer peripheral part of the element is composed of a drive arm and a weight part, and thus there is a problem that it is difficult to hold the element.

  In addition, since the portion where the vibrator (element) and the support base (lower lid) are joined is small, the strength of the laminated structure including the vibrator and the support base is reduced, and the wafer made of the laminated structure is likely to be damaged. There was a problem.

  Accordingly, the present invention provides an inertial force sensor including a detection element, wherein the detection element includes a first substrate, a second substrate provided on the first substrate, and an upper surface of the second substrate. A third substrate provided on the substrate, a third substrate comprising: a support portion; an arm portion connected to the support portion; a weight portion connected to the arm portion; and a peripheral portion provided around the arm portion. It is set as the structure which has these.

  According to the present invention, since the peripheral portion is bonded to the substrate and the lower lid, the strength of the wafer composed of a plurality of vibrators is improved, and damage to the wafer in the manufacturing process can be suppressed.

The perspective view of the detection element with which the inertial force sensor of Embodiment 1 is provided Top view of the detector The figure which expanded a part of detection element of Drawing 2 FIG. 2 is an enlarged view of a part of the detection element of FIG. Schematic diagram showing the operating principle of the detector Another top view of the detector

  Hereinafter, an inertial force sensor according to an embodiment of the present invention will be described with reference to the drawings. In addition, in each drawing, the provision of the code | symbol with respect to the same part may be abbreviate | omitted, and the description may be abbreviate | omitted suitably. Each drawing shows an example of a preferable form, and is not limited to each configuration, shape, and numerical value. Moreover, it is possible to combine suitably each element technology demonstrated in embodiment in the range without a contradiction.

  1 is a perspective view showing a detection element 2 for detecting an angular velocity which is a kind of inertial force, FIG. 2 is a top view of the detection element 2, and FIG. 3 is an enlarged view of a broken line part of FIG. is there.

  The detection element 2 has a structure in which a first substrate 2a, a second substrate 2b, and a third substrate 2c are stacked.

  The first substrate 2a is formed using a single crystal silicon substrate. A single crystal silicon substrate has characteristics that it is easy to process, that the surface is smooth, and that it is easy to obtain flatness, and that it can be easily joined to other substrates. However, the first substrate 2a is not limited to a single crystal silicon substrate. For example, a single crystal substrate such as a crystal or magnesium oxide single crystal substrate, an amorphous substrate such as a glass substrate or a quartz substrate, or a ceramic substrate such as alumina or zirconium may be used.

  The second substrate 2b is preferably a substrate made of the same material as the first substrate 2a. This is because the bonding to the first substrate 2a and the third substrate 2c can be performed with high accuracy, but a substrate made of a material different from that of the first substrate 2a may be used. The second substrate 2b is formed using, for example, a single crystal substrate or a glass substrate.

  Furthermore, the first substrate 2a and the second substrate 2b may be formed of the same substrate. Specifically, the first substrate 2a is processed, and the first substrate 2a is provided with a concavo-convex shape at a necessary portion. Two structures of 2a and the second substrate 2b can be realized by one substrate.

  The third substrate 2c is formed using a single crystal silicon substrate. This is because the single crystal silicon substrate has a high processing accuracy and can form a structure which becomes a vibrator of the angular velocity sensor with high accuracy. However, the material of the third substrate 2c is not limited to a single crystal silicon substrate. For example, a single crystal substrate other than silicon, an amorphous substrate such as a glass substrate or a quartz substrate, or a ceramic substrate such as alumina or zirconium can be used.

  Note that the detection element 2 can also be configured using an SOI substrate. In this case, the first substrate 2a is composed of silicon, the second substrate 2b is composed of a buried oxide film (silicon oxide film), and the third substrate 2c is composed of silicon.

  Further, in the SOI substrate, the detection element 2 can be configured using a substrate on which the first substrate 2a and the second substrate 2b are processed in advance.

  The 3rd board | substrate 2c has the support part 6, the arm part 8, the drive part 10, the detection part 11, the monitor part (not shown), the peripheral part 16a, and the peripheral part 16b.

  The support portion 6 is a rectangular portion provided at the center of the third substrate 2c. In the support portion 6, the third substrate 2c and the second substrate 2b are connected.

  The support portion 6 is provided at the center of the third substrate 2c in a top view. The support unit 6 includes a first electrode 18a connected to the drive unit 10, a second electrode 18b connected to the detection unit 11, a third electrode 18c connected to the monitor unit, and a fourth electrode for supplying a reference potential. Electrode 18d. In FIG. 2, as an example, two each of the first electrode 18 a, the second electrode 18 b, and the third electrode 18 c are provided on the support portion 6, and the fourth electrode 18 d is provided on one support portion 6. The case where it provides is shown in figure.

  As shown in FIG. 4, the arm portion 8 includes a first portion 8a, a second portion 8b, a third portion 8c, a fourth portion 8d, a fifth portion 8e, a sixth portion 8f, and a seventh portion. Part 8g.

  In another expression, the arm portion 8 includes a pair of beams extending in the Y-axis direction with the support portion 6 as a center, and a pair of arm portions 8 connected to the distal ends of the beams.

  The first portion 8a extends from the support portion 6 in the Y-axis direction. The second portion 8b extends from the first portion 8a in the X-axis direction. The third portion 8c extends from the second portion 8b in the Y-axis direction. The fourth portion 8d extends from the third portion 8c in the X-axis direction. The fifth portion 8e extends from the fourth portion 8d in the Y-axis direction. The sixth portion 8f extends from the fifth portion 8e in the X-axis direction. The seventh portion 8g extends in the Y-axis direction from the sixth portion 8f.

  Further, when the structure including the first portion 8a to the sixth portion 8f is the first structure, the third substrate 2c is a second symmetrical to the first structure with respect to L1 in FIG. 3, a third structure symmetrical to the first structure with respect to L2 in FIG. 3, and a fourth structure symmetrical to the second structure with respect to L1 in FIG. 3. Here, L1 is a virtual line passing through the center of the support portion 6 and parallel to the X axis. L2 is an imaginary line passing through the center of the support 6 and parallel to the Y axis.

  In another expression, the arm portion 8 has a plurality of bent portions that are bent in the XY plane, and has an annular structure that surrounds the support portion 6. Here, the “bent portion” means a portion where the first portion 8a and the second portion 8b are connected, a portion where the second portion 8b and the third portion 8c are connected, and a third portion. A portion where 8c and the fourth portion 8d are connected, a portion where the fourth portion 8d and the fifth portion 8e are connected, a portion where the fifth portion 8e and the sixth portion 8f are connected, The sixth portion 8f is connected to the seventh portion 8g.

  In addition, the arm part 8 does not need to have all from the 1st part 8a to the 7th part 8g. For example, the third portion 8c to the fifth portion 8e may be omitted.

  Note that the arm portion 8 may be configured to have more portions in addition to the first portion 8a to the seventh portion 8g.

  FIG. 4 is an enlarged view of a part of FIG.

  The peripheral edge portion 16a (first peripheral edge portion) is a portion provided outside the arm portion 8, and is a portion that does not contribute to detection of inertial force. The peripheral edge portion 16 a is a separate body separated from the support portion 6, the arm portion 8, and the weight portion 9. The combined shape of the peripheral edge portion 16a and the weight portion 9 is a square shape when viewed from above.

  The peripheral edge portion 16 a has a portion facing the arm portion 8 and a portion facing the weight portion 9. A gap having a width W1 is provided between the peripheral edge portion 16a and the weight portion 9. The width between the peripheral portion 16a and the second portion 8b is equal to the width between the peripheral portion 16a and the sixth portion 8f. This width is W2. A gap having a width W3 is provided between the peripheral edge portion 16a and the seventh portion 8g. The peripheral edge 16b (second peripheral edge) has a symmetrical structure with respect to the first peripheral edge 16a and L1.

  Here, W1, W2, and W3 are set to be substantially equal. If the dimensions of W1, W2, and W3 are equal, the microloading effect can be suppressed and the vibrator can be processed with high accuracy in the Si dry etching process for forming the vibrator.

Preferably, when the arm width of the vibrator and the dimensions of W1, W2, and W3 are the same, the line and space ratio during dry etching becomes constant, and the vibrator can be processed with higher accuracy.
(Supplement: The microloading effect is a phenomenon in which the etching rate decreases when the width of the pattern to be processed by dry etching decreases (or the aspect ratio of the etched portion: the pattern width / etching depth increases). (If there is a pattern with different speed, the processing shape by etching will deteriorate)
In addition, when the vibrator is vibrating (driven), the drive arm of the vibrator may be over-amplified due to disturbance factors such as external impact. Therefore, the reliability of the vibrator can be improved.

  The arm unit 8 is provided with a drive unit 10, a detection unit 11, and a monitor electrode unit (not shown).

FIG. 5 is a diagram for explaining the operating principle of the detection element 2.
Each of the drive unit 10 and the detection unit 11 includes an upper electrode 12 made of Au or the like, a lower electrode 13 made of Pt or the like, and a piezoelectric body 14 made of lead zirconate titanate or the like disposed therebetween. It has a laminated structure.

  Here, when a positive voltage is applied to the upper electrode 12 in a state where the lower electrode 13 is connected to the ground, a compressive force is exerted in the electrode stacking direction. This compressive force generates stress in the direction in which the electrode extends. When a negative voltage is applied to the upper electrode 12 with the lower electrode 13 connected to the ground, a tensile force acts on the electrode. This tensile force generates stress in the direction in which the electrode pattern shrinks.

  On the contrary, a negative voltage is generated when the arm portion 8 is bent and compressive stress is generated in the electrode. A positive voltage is generated when tensile stress is generated in the electrode.

  By applying a drive signal from the IC (not shown) to the drive unit 10, the weight unit 9 vibrates in the X-axis direction (arrow A1 in FIG. 2). Hereinafter, this vibration is referred to as “drive vibration”. In a state where driving vibration is generated, a Coriolis force is generated in the detection element 2 by applying an angular velocity around the Z axis orthogonal to the vibration plane (XY plane). This Coriolis force causes the weight portion 9 to detect vibration in the Y-axis direction as indicated by an arrow 16 (arrow A2 in FIG. 2), and the deflection of the arm portion 8 due to this detected vibration is converted into an electrical signal by the detection portion 11 and converted to an IC Output.

  The monitor electrode 17 is provided in the vicinity of the connecting beam 7 of the arm portion 8. The vibration state of the drive vibration of the arm unit 8 is detected and fed back to the generation of the drive signal in the IC.

  FIG. 6 is a top view of another detection element 20 provided in the inertial force sensor of the present embodiment.

  The detection element 20 is different from the detection element 20 in that the detection element 20 includes a peripheral edge portion 16c (first peripheral edge portion), a peripheral edge portion 16d (second peripheral edge portion), a peripheral edge portion 16c (third peripheral edge portion), and a peripheral edge. It is a point provided with the part 16d (4th peripheral part).

  In the above description, the example in which the detection element is driven and vibrated using the piezoelectric body has been described. However, the present invention is not limited to this. For example, a first comb-shaped electrode may be provided on the weight portion 9, and driving vibration may be generated by applying an electrostatic force to the first comb-shaped electrode. In addition, although the example which converts a detection vibration into an electric signal using a piezoelectric material was demonstrated, it is not restricted to this. For example, the weight portion 9 may be provided with a second comb-tooth electrode, and the detected vibration may be converted into an electric signal based on a change in capacitance accompanying the displacement of the second comb-tooth electrode.

  The detection element 2 and the IC are mounted on a package (not shown) made of, for example, ceramic. The detection element 2, IC, package, and inertial force sensor are configured.

  The present invention is useful, for example, in an electronic device in which a small and highly accurate inertial force sensor is required.

2, 20 detection element 2a first substrate 2b second substrate 2c third substrate 6 support portion 8 arm portion 8a first portion 8b second portion 8c third portion 8d fourth portion 8e fifth Part 8f 6th part 8g 7th part 9 Weight part 10 Drive part 11 Detection part 12 Upper electrode 13 Lower electrode 14 Piezoelectric body 16a, 16b, 16c, 16d, 16e, 16f Peripheral part

Claims (6)

An inertial force sensor including a detection element,
The detection element includes a first substrate, a second substrate provided on the first substrate, and a third substrate provided on the second substrate,
The third substrate is an inertial force sensor having a support part, an arm part connected to the support part, a weight part connected to the arm part, and a peripheral part provided around the arm part. The support portion is provided at the center of the third substrate in a top view,
The inertial force sensor according to claim 1, wherein the peripheral portion has a portion facing the arm portion and a portion facing the weight portion. The inertial force sensor according to claim 1, wherein the peripheral portion is a separate body separated from the support portion, the arm portion, and the weight portion. The inertial force sensor according to claim 1, wherein the shape of the peripheral portion and the weight portion is a square shape when viewed from above. An IC electrically connected to the detection element;
The inertial force sensor according to claim 1, further comprising a package for mounting the detection element and the IC. The inertial force sensor according to claim 1, wherein the inertial force is an angular velocity.

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